NS334 is a tungsten-containing nickel-chrome-molybdenum alloy with lower silicon and carbon, which is considered to be a versatile corrosion resistant alloy. It is currently the most corrosion-resistant alloy. High molybdenum composition makes it resist localized corrosion, such as pitting. The lower carbon minimizes the carbide precipitation during the welding process so as to maintain the resistance to intergranular corrosion of the hot metamorphic part at the welding interface. Although the C-276 alloy will eventually become brittle and precipitate in the high temperature, it also has good high temperature strength and moderate oxidation resistance. Alloy C-276 has been used for many years and is used in construction projects related to ASME Boiler and Pressure Vessel Code. It is mainly resistant to wet chlorine, various oxidizing chlorides, chloride salt solutions, sulfuric acid and oxidizing salt. It has good corrosion resistance in low temperature and middle temperature hydrochloric acid. Therefore, it is widely used in Chemical industry, Petrochemical industry, flue gas desulfurization, pulp and paper industry, environmental protection and etc industrial fields in the harsh corrosion environment during the past 30 years.

It has the following properties:

• In oxidation and reduction two atmosphere state, has excellent corrosion resistance to most corrosive media.
• It has excellent pitting corrosion resistance, crevice corrosion and stress corrosion resistance. The higher content of Mo and Cr make the alloy resistant to chloride ion corrosion, and the W element further improves the corrosion resistance. At the same time, Hastelloy C-276 alloy is one of the only several materials resistant to the corrosion of humid chlorine gas, hypochlorite and chlorine dioxide solutions, and has significant corrosion resistance to high concentration of chloride salt solutions such as ferric chloride and copper chloride. Suitable for sulfuric acid solution of various concentrations, it is one of the few materials that can be used in hot concentrated sulfuric acid solution.

Process Performance and Requirements

• Product Fusion Process

Vacuum Induction Furnace(VIM) and Electroslag Remelting Furnace(ESR)

• Product Chemical Composition

• Product Physical Property

• Product Mechanical Property

• Product Heat Treatment Institution

1,Heating

The material is heated in a vacuum furnace and the temperature is controlled on about 1150°C. When the temperature reaches the required level (about 1100°C), begin to hold heating for a period. If the material's thermal conductivity is poor, then take other protective measures.

2,Heat Preservation

The material can be cooled to room temperature or lower in the vacuum furnace. It also can be by quenching treatment to improve Hastelloy C-276 hardness, wear resistance and fatigue strength. Quenching technological parameter: heating heating≤30°Ch/s (i.e. temperature rise per hour <30 ℃); Cooling rate ≤5°Ch/s (i.e. temperature falling <5℃).

3,Tempering

In order to eliminate the stress caused by quenching, the material needs to be tempered. The tempering technological parameter: the heating rate is 20~30°Ch/s; (i.e. temperature rise per hour from 20℃ to 30℃ ); The cooling rate is less than 10~20°Ch/s. (i.e.temperature falling per hour is 10℃ to 20℃).

4,Cold treatment

In order to eliminate the residual stress in Hastelloy C-276, reduce the hardness and the embrittlement layer depth,that cold treatment is needed. There are two cold treatment methods: demagnetization and ageing.

• Productive Process

• Professional Customization